1. Field of the Invention
The present invention relates in general to an image display apparatus for introducing a light beam into the pupil of a viewer, and for projecting an image onto the retina of the viewer with the light beam introduced, for thereby permitting the viewer to view a virtual image in front of the pupil.
2. Description of the Related Art
Recently, various image display apparatuses have been devised, each of which introduces a light beam into the pupil of a viewer, and which projects an image onto the retina of the viewer with the light beam introduced, for thereby permitting the viewer to view a virtual image in front of the pupil. They are each referred to as “Retinal Scanning Display.”
Japanese Patent No. 2874208 discloses an example of a conventional image display apparatus of the type described above. This example is an apparatus with a plurality of components thereof for displaying an image for a viewer.
The above example of the conventional image display apparatus is constructed to include: (a) a light source for emitting a light beam and permitting modulation of the intensity of the emitted light beam; (b) a wave-front-curvature modulator for modulating the curvature of a wave front of the light beam emitted from the light source; (c) a deflector for deflecting the light beam; (d) an optical path element for letting the light beam propagate between the aforementioned plurality of components; and (e) an optical system for letting the light beam enter the viewer's pupil.
The optical system mentioned above is designed to cause the light beam to enter the pupil, after the light beam is modulated by the corresponding components with respect to the angle of the light beam incident to the pupil; and with respect to the curvature of the wave front and the intensity of the light beam.
Furthermore, the thus exemplified image display apparatus is used such that the light beam is scanned by the above deflector, and such that the scanned light beam enters the retina of the viewer's eye, resulting in a direct projection of an image onto the retina.
Eventually, the exemplified image display apparatus allows the viewer to view a virtual image in front of the pupil in the direction of a line defined by extending back the light beam entering the pupil. It is therefore followed that the direction of the light beam entering the pupil determines a display direction in which a virtual image is displayed relative to the viewer.